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// Copyright (C) 2018 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#include "qwasmopenglcontext.h"
#include "qwasmintegration.h"
#include <EGL/egl.h>
#include <emscripten/val.h>
QT_BEGIN_NAMESPACE
QWasmOpenGLContext::QWasmOpenGLContext(const QSurfaceFormat &format)
: m_requestedFormat(format)
{
m_requestedFormat.setRenderableType(QSurfaceFormat::OpenGLES);
// if we set one, we need to set the other as well since in webgl, these are tied together
if (format.depthBufferSize() < 0 && format.stencilBufferSize() > 0)
m_requestedFormat.setDepthBufferSize(16);
if (format.stencilBufferSize() < 0 && format.depthBufferSize() > 0)
m_requestedFormat.setStencilBufferSize(8);
}
QWasmOpenGLContext::~QWasmOpenGLContext()
{
if (m_context) {
// Destroy GL context. Work around bug in emscripten_webgl_destroy_context
// which removes all event handlers on the canvas by temporarily removing
// emscripten's JSEvents global object.
emscripten::val jsEvents = emscripten::val::global("window")["JSEvents"];
emscripten::val::global("window").set("JSEvents", emscripten::val::undefined());
emscripten_webgl_destroy_context(m_context);
emscripten::val::global("window").set("JSEvents", jsEvents);
m_context = 0;
}
}
bool QWasmOpenGLContext::isOpenGLVersionSupported(QSurfaceFormat format)
{
// Version check: support WebGL 1 and 2:
// (ES) 2.0 -> WebGL 1.0
// (ES) 3.0 -> WebGL 2.0
// [we don't expect that new WebGL versions will be created]
return ((format.majorVersion() == 2 && format.minorVersion() == 0) ||
(format.majorVersion() == 3 && format.minorVersion() == 0));
}
bool QWasmOpenGLContext::maybeCreateEmscriptenContext(QPlatformSurface *surface)
{
// Native emscripten/WebGL contexts are tied to a single screen/canvas. The first
// call to this function creates a native canvas for the given screen, subsequent
// calls verify that the surface is on/off the same screen.
QPlatformScreen *screen = surface->screen();
if (m_context && !screen)
return false; // Alternative: return true to support makeCurrent on QOffScreenSurface with
// no screen. However, Qt likes to substitute QGuiApplication::primaryScreen()
// for null screens, which foils this plan.
if (!screen)
return false;
if (m_context)
return m_screen == screen;
m_context = createEmscriptenContext(QWasmScreen::get(screen)->canvasTargetId(), m_requestedFormat);
m_screen = screen;
return true;
}
EMSCRIPTEN_WEBGL_CONTEXT_HANDLE QWasmOpenGLContext::createEmscriptenContext(const QString &canvasTargetId, QSurfaceFormat format)
{
EmscriptenWebGLContextAttributes attributes;
emscripten_webgl_init_context_attributes(&attributes); // Populate with default attributes
attributes.powerPreference = EM_WEBGL_POWER_PREFERENCE_HIGH_PERFORMANCE;
attributes.failIfMajorPerformanceCaveat = false;
attributes.antialias = true;
attributes.enableExtensionsByDefault = true;
attributes.majorVersion = format.majorVersion() - 1;
attributes.minorVersion = format.minorVersion();
// WebGL doesn't allow separate attach buffers to STENCIL_ATTACHMENT and DEPTH_ATTACHMENT
// we need both or none
bool useDepthStencil = (format.depthBufferSize() > 0 || format.stencilBufferSize() > 0);
// WebGL offers enable/disable control but not size control for these
attributes.alpha = format.alphaBufferSize() > 0;
attributes.depth = useDepthStencil;
attributes.stencil = useDepthStencil;
QByteArray convasSelector = canvasTargetId.toUtf8();
EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context = emscripten_webgl_create_context(convasSelector.constData(), &attributes);
return context;
}
QSurfaceFormat QWasmOpenGLContext::format() const
{
return m_requestedFormat;
}
GLuint QWasmOpenGLContext::defaultFramebufferObject(QPlatformSurface *surface) const
{
return QPlatformOpenGLContext::defaultFramebufferObject(surface);
}
bool QWasmOpenGLContext::makeCurrent(QPlatformSurface *surface)
{
bool ok = maybeCreateEmscriptenContext(surface);
if (!ok)
return false;
return emscripten_webgl_make_context_current(m_context) == EMSCRIPTEN_RESULT_SUCCESS;
}
void QWasmOpenGLContext::swapBuffers(QPlatformSurface *surface)
{
Q_UNUSED(surface);
// No swapbuffers on WebGl
}
void QWasmOpenGLContext::doneCurrent()
{
// No doneCurrent on WebGl
}
bool QWasmOpenGLContext::isSharing() const
{
return false;
}
bool QWasmOpenGLContext::isValid() const
{
if (!(isOpenGLVersionSupported(m_requestedFormat)))
return false;
// Note: we get isValid() calls before we see the surface and can
// create a native context, so no context is also a valid state.
return !m_context || !emscripten_is_webgl_context_lost(m_context);
}
QFunctionPointer QWasmOpenGLContext::getProcAddress(const char *procName)
{
return reinterpret_cast<QFunctionPointer>(eglGetProcAddress(procName));
}
QT_END_NAMESPACE
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